With request for higher qualities of polymeric materials, materials having multiple properties, in some cases, materials having combined properties opposite to each other have been required. In particular, in the field of industrial polymeric materials, materials having combined properties (e.g., high rigidity and impact resistance, flexibility and chemical resistance, or abrasion resistance and oil resistance) have been demanded, and the development of compositions obtained by combining various resins with vulcanized rubbers (or rubbers) has been desired.
However, materials having different properties are not usually compatible with each other, so that simple mixing of both the materials only obtains a mixture in which one component is inhomogeneously dispersed in the other. Therefore, it is difficult to give a composition having such a new property as to be a combination of properties of both the materials. If anything, such a mixture often entails deterioration in important properties as an industrial material (e.g., breaking elongation (or elongation at break), cold resistance), and in many cases it cannot become practicable technique. These defects are solved by firmly bonding the interfaces of both the components to each other in mixing of the both to give a similar effect in as the case the both being substantially compatible with each other at the interfaces.
To date, many methods for obtaining a composite of a resin member bonded to a rubber member have been proposed. In mixing a resin and a rubber, it is considered that utilization of these composite techniques ensure a new composition (composite dispersion) in which one component is dispersed in the other component uniformly and both the interfaces are enough bonded to express both properties in combination.
As a process for obtaining a composite of a rubber member bonded to a resin member, for example, a process which comprises bonding both the members by an adhesive has been known. However, in the case obtaining a composite by utilizing an adhesive, it is necessary to interpose the adhesive between the resin and the rubber intensively. However, in mixing of these three components, it is difficult to interpose the adhesive only in the interface of the rubber and the resin, and throughout the interface.
Moreover, a method bonding a resin-molded member to a rubber-molded member directly has been proposed. For example, Japanese Patent Application Laid-Open No. 25682/1975 (JP-50-25682A) discloses a process for producing a composite, which comprises rubbing a thermoplastic plastic and a vulcanized rubber compatible with the thermoplastic plastic with contacting each other to melt or fuse the surface of the plastic, and solidifying the resultant mixture with contacting the thermoplastic resin component and the vulcanized rubber component. However, in the process, it is difficult to produce an object composite.
Japanese Patent Application Laid-Open No. 124803/1997 (JP-9-124803A) discloses a process for producing a composite member, which comprises heating an acrylonitrile-containing thermoplastic resin (e.g., AS resin, ABS resin, etc.) with an acrylonitrile-containing rubber with intimately contacting each other through the use of compatibility between the thermoplastic resin and the rubber. However, this process markedly restricts species of resins and rubbers because both of them should contain acrylonitrile, and therefore the practical applications are much limited. 
Japanese Patent Application Laid-Open No. 156188/1996 (JP-8-156188A) discloses a process for producing a composite member, which comprises vulcanizing an epoxy group-containing resin composition which establishes contact with an elastic rubber having a vulcanized carboxyl group or an acid anhydride group, and bonding the contact surface between the resin composition and the rubber through the use of a chemical reaction of an epoxy group with a carboxyl group. However, since this process uses the chemical reaction of the epoxy group with the carboxyl group, species of the resin and the rubber are markedly limited, and it is difficult to obtain composites widely.
Japanese Patent Application Laid-Open No. 150439/1990 (JP-2-150439A), Japanese Patent Application Laid-Open No. 133631/1991 (JP-3-133631A) and Japanese Patent Application Laid-Open No. 138114/1991 (JP-3-138114A) propose a process for producing a composite, which comprises vulcanizing a polyamide-series resin and a rubber component in the presence of a vulcanizing system, wherein the rubber component comprises a carboxyl group- or an acid anhydride group-containing rubber, a peroxide, a vulcanization-activating agent (e.g., ethylene glycol dimethacrylate, triallyl isocyanurate, etc.), and an alkoxysilane compound. In these documents, a polyamide-series resin containing the larger number of a terminal amino group than that of a terminal carboxyl group is mostly used as an aliphatic polyamide-series resin. That is, this process utilizes a reaction of an amino group with a carboxyl group or an acid anhydride group. Therefore, the species of resins and that of rubbers are markedly restricted, and it is difficult to obtain a resin-rubber composite in a wide range of the resin and the rubber.
Japanese Patent Application Laid-Open No. 11013/1995 (JP-7-11013A) discloses a process for producing a composite member of a vulcanized rubber and a polyamide molded article, by bringing a polyamide molded article into contact with a rubber compound containing a rubber, a peroxide vulcanizing agent and a silane compound and by vulcanizing them.
However, the process does not only require a silane compound but also restricts the resin to a polyamide-series resin, so that the process also has no versatility.
On the other hand, Japanese Patent Application Laid-Open No. 30221/2002 (JP-2002-30221A) discloses a thermoplastic resin composition in which a vulcanized rubber (A) is dispersed in the form of particle in a continuous phase of a thermoplastic resin (B), wherein the rubber (A) and the thermoplastic resin (B) include combinations in which a resin molded article and a rubber molded element comprising the rubber (A) are capable of adhering at such a degree of an adhesive strength that a cohesive failure occurs in a peel test, when the rubber (A) is vulcanized with bringing the resin molded article comprising the thermoplastic resin (B) into contact with the unvulcanized rubber (A) under pressure and heating.
This literature describes, as concrete combinations of a resin and a rubber in which a cohesive failure occurs, (1) a combination of at least one rubber selected from the group consisting of SBR, NR, EPDM, an acid-modified ethylene-propylene rubber and an ethylene-acrylic acid-acrylate copolymer rubber, and a polyphenylene ether (PPE) or a composition thereof; and (2) a combination of at least one rubber selected from the group consisting of an acid-modified ethylene-propylene rubber, an acid-modified nitrile rubber and a fluorine-containing rubber, and a thermoplastic resin having an amino group. Further, the reference describes that an organic peroxide is used as a rubber-vulcanizing agent in many cases, and the PPE composition may comprise 100 parts by weight of the PPE, 0 to 30 parts by weight of a polyalkenylene, and 0 to 30 parts by weight of a styrenic rubber, in the combination (1) of the PPE or the composition thereof. Moreover, it is mentioned in the literature that about 0.1 to 5 parts by weight of a vulcanization accelerator (e.g., a benzothiazole compound, triallylisocyanurate, m-phenylenebismaleimide, trimethylolpropane tri(meth)acrylate), or about 0.5 to 12 parts by weight of a polyalkenylene (e.g., a polyoctenylene) as a processing synergist is added to 100 parts by weight of the rubber.
However, in a method mentioned in the literature, it is difficult to find a combination of a resin and a rubber with a cohesive failure, and the combination of the resin and the rubber is significantly restricted. Moreover, even when such a combination is selected, an adhesive strength between a continuous phase and a dispersed phase is not enough in many cases.
It is therefore an object of the present invention to provide a composite dispersion (or a composited dispersion) which comprises a continuous phase comprising a resin, and a dispersed phase being bonded to the continuous phase and comprising a vulcanized rubber in a wide range of combination of the resin and the rubber, and a process for producing the same.
It is another object of the present invention to provide a process for producing a composite dispersion, by a convenient process, which comprises a resin phase and a vulcanized rubber phase being firmly bonded to the resin phase.
It is still another object of the present invention to provide a composite dispersion capable of imparting a rubber property to a resin matrix effectively, and a process for producing the same.
It is a further object of the present invention to provide a molded article formed from a composite dispersion which comprises a resin phase and a vulcanized rubber phase being firmly bonded to the resin phase.